At present, compared with liquid crystal display devices (LCDs), organic electroluminescent display devices (OLEDs) have characteristics such as fast response, wide color gamut, ultrathin thickness and capability of flexibility, and therefore gradually become the main stream in display field.
The structure of an OLED display device mainly comprises: a base substrate, an organic electroluminescent pixel array fabricated on the base substrate, wherein each organic electroluminescent pixel array comprises an anode and a cathode disposed oppositely and a luminescent layer between the anode and the cathode. The OLED display device implements light emission by exciting the organic material in the luminescent layer to emit light through the recombination of electrons in the cathode and holes in the anode in the luminescent layer.
At present, there are five methods for OLED display devices to implement full color display, namely red, green and blue pixels side-by-side pixelation (RGB-SBS), color conversion method, color filter method, resonant cavity color tuning method and multi-layer stack method. The color filter method uses the full color display principle of liquid crystal displays, wherein white light is emitted by means of an OLED and then filtered to obtain three primary colors by the color filter. However, in this type of display structure, most light energy of the white light is absorbed by the color filter, resulting in a low transmittance. Therefore, it is difficult to display white pictures with high luminance, which causes the OLED display device can not display images with high contrast and further increases power consumption of the OLED display device.
Therefore, in order to improve luminance and reduce power consumption of an OLED display device, an OLED display device with RGBW pixel structure has been manufactured as shown in FIG. 1. In the OLED display device of such a structure, a pixel unit 1 comprises sub-pixel units 01 displaying RGBW four colors. Since the light transmittance in the sub-pixel units 01 for displaying white is much higher than that in the sub-pixel units 01 for displaying red, green or blue, gray luminance of each pixel unit is determined by the sub-pixel unit 01 for displaying white in this pixel unit. Gray luminance of a pixel unit refers to the luminance of a pixel unit during the luminance transitions from white (black) to black (white). Compared with OLED display devices with RGB pixel structure, OLED display devices with RGBW pixel structure can enhance luminance of OLED display devices. However, in OLED display devices of RGBW pixel structure, since in operation, the sub-pixel units displaying white is constantly emitting light in comparison to the sub-pixel units displaying red, green or blue, the lifetime of the sub-pixel units displaying white will be reduced, thereby reducing the lifetime of the entire OLED display device.